Faulted circuit indicators (FCIs) are well known in the field of electric power distribution systems. Generally, FCIs are electrically connected to transmission lines in a power distribution system at various locations throughout the system, often in close proximity to system loads. When a fault occurs in a transmission line, FCIs between the power source and the fault will detect that a fault has occurred. Typically, FCIs that have detected a fault then display an indication that the fault has been detected. A technician can then identify a fault by locating the transmission line between an FCI that indicates it has detected a fault and an FCI that displays no such indication.
Most FCIs are capable of displaying only a binary result: whether the FCI has detected a fault or not. Prior art FCIs cannot display to a technician the present state of the transmission lines to which the FCIs are attached, other than to display that a fault has passed through that line.
Modern power distribution systems may have multiple sources of electricity (or “feeds”) for a particular transmission line. Simply turning off a single feed circuit to a particular portion of a transmission line may not guarantee that a particular line is de-energized. Furthermore, in some three-phase power systems, one phase may fault and trip an FCI, while the other phases remain energized. Thus, technicians must carry additional equipment to determine whether a particular transmission line is de-energized, and cannot safely rely solely on a fault indication from a prior art FCI.
Further, because of their binary nature, prior art FCIs provide little assistance in locating a transient or intermittent fault. Generally, prior art FCIs are reset either by a manual trigger, wherein a technician manually manipulates the FCI to remove the fault indication, or by a current trigger, wherein if the FCI determines that conditions on the transmission line have returned to normal, the FCI automatically resets. In the prior art, an automatic reset is a desirable feature because it ensures that the FCI only indicates existing faults, which reduces the likelihood that a false fault indication will increase the amount of time necessary for a technician to diagnose and repair an actual fault. The result of an automatic reset is, however, that an intermittent or transient fault would trigger an FCI's indicator only for a short time, followed by an immediate reset of the indicator, making the location of a faulted FCI during the presence of a faulted condition nearly impossible.
Moreover, prior art FCIs cannot monitor other conditions on a transmission line that may pose risks to the life or performance of the transmission line and other related equipment. For example, power surges at certain levels may not be sufficient to result in a fault condition that would be indicated by present FCIs, but may shorten the life of a transmission line that experiences those surges and any transformers or other equipment attached to that line. Additionally, conditions such as excess heat or vibration on a line may be indicative of a problem on a transmission line that, with the use of present FCIs, cannot be detected until a fault occurs, potentially resulting in a loss of service for customers that might have been avoided had the condition been diagnosed earlier.
Finally, when a fault occurs, the only way of determining which portion of transmission line that contains the fault is to send technicians to the general vicinity of a power outage to search for FCIs that indicate a fault. Because transmission lines are often located underground, this may require the technicians to travel from FCI to FCI on foot until the first faulted FCI is located. Thus, even with the help of FCIs, the process of locating a fault can be time consuming, resulting in increased costs to the electrical utility company servicing the fault, as well as extended periods of outages for their customers.
Prior art systems address the above problems through the use of additional equipment, such as meters, that are carried by repair and maintenance personnel working for utility companies. Unfortunately, these solutions do not address the issues of transient fault location, constant line monitoring for unfavorable conditions, or improved response time when a fault has occurred. Further, because of the need for handheld equipment, a technician must still approach a transmission line that has been indicated as faulted to determine if the line is energized, and therefore unsafe for repair work.
Accordingly, there is a need to overcome the limitations of the prior art by developing an FCI that is capable of displaying the present state of a transmission line. Beyond the need for displaying the present state of a transmission line, FCIs should also be capable of monitoring line conditions aside from simple current flow to assist in the determination of unfavorable conditions, storing historical fault and line state information to assist in the diagnosis of transient and intermittent faults, and communicating fault and line state information to a remote location to reduce the time needed to recover from a fault event.